A digital photographing apparatus is provided including a lens unit, an imaging device, and a main mirror disposed between the lens unit and the imaging device, wherein the position of the main mirror can be changed so that the main mirror either reflects at least part of light which passed through the lens unit toward a first orientation or the main mirror is not positioned on a path of the light which passed through the lens unit such that the light can be incident to the imaging device. A prism unit, a viewfinder, and an image sensor for live view are also included in the apparatus. A method of controlling the digital photographing apparatus, and a storage medium having recorded thereon a computer program for executing the method are also provided.